The transfer of adipose tissue to various regions of the body is a relatively common cosmetic, therapeutic and structural procedure involving the harvest of adipose tissue from one location and re-implantation of the harvested and, oftentimes processed tissue, in another location (see Coleman 1995; and Coleman 2001). While being largely used for repair of small cosmetic defects such as facial folds, wrinkles, pock marks and divots; the transfer of adipose tissue has recently been used for cosmetic and/or therapeutic breast augmentation and reconstruction (Bircoll and Novack 1987; and Dixon 1988), and augmentation of the buttocks (Cardenas-Camarena, Lacouture et al. 1999; de Pedroza 2000; and Peren, Gomez et al. 2000).
In the past, adipose tissue grafts and methods of adipose tissue transfer have been plagued with difficulties and side effects including necrosis, absorption of the implant by the body, infection (Castello, Barros et al. 1999; Valdatta, Thione et al. 2001), calcifications and scarring (Huch, Kunzi et al. 1998), inconsistent engraftment, (Eremia and Newman 2000), lack of durability, and other problems arising from lack of neovascularization and necrosis of the transplanted tissue. One of the biggest challenges in adipose tissue transfer is absorption of the implant by the body and volume retention of adipose tissue grafts following transfer. When adipose tissue is harvested or washed, the space between individual pieces of harvested adipose tissue is filled by liquid (e.g., water, blood, tumescent solution, oil). When this tissue/fluid mixture is implanted into a recipient the liquid portion is rapidly absorbed by the body resulting in loss of volume. The process by which the amount of fluid is removed from the tissue/fluid mixture is frequently referred to as “drying the adipose tissue” or “dehydrating the adipose tissue”. The content of red and white blood cells and the like within an adipose tissue graft can also significantly affect the volume of graft retained after graft transplantation, due to induction or exacerbation of an inflammatory response. Another aspect of tissue retention relates t the amount of lipid within the adipose tissue graft. It understood that the presence of free lipid (meaning lipids released from dead or damaged adipocytes; also referred to as oil) in adipose tissue grafts can result in induction or exacerbation of an inflammatory response with substantial phagocytic activity and consequent loss of graft volume.
It is also known that mixing unprocessed adipose tissue with a concentrated population of adipose-derived regenerative cells overcomes many of the problems associated with adipose tissue grafts and adipose tissue transfer, as described above. Specifically, supplementing unprocessed adipose tissue with concentrated populations of adipose-derived cells comprising adipose-derived stem cells increases the weight, vascularization, and retention of fat grafts. (See U.S. Pat. No. 7,390,484 and co-pending U.S. Patent Application Publication No. 2005/0025755, herein expressly incorporated by reference in their entireties). Adipose tissue fragments supplemented, or mixed, with a concentrated population of cells including adipose-derived stem cells exhibit improved neoangiogeneis and perfusion in grafts when compared to unsupplemented grafts of adipose tissue alone in animal models. Further, adipose tissue grafts supplemented with adipose-derived regenerative cells that comprise adipose derived stem cells show increased graft retention and weight over time, when compared to unsupplemented grafts. (See U.S. Patent Application Publication No. 2005/0025755). Further, the processing of adipose tissue in a closed, sterile fluid pathway greatly reduces the chance of infection. The improvement in autologous transfer of adipose tissue seen in the animal models described above has also been replicated in human clinical studies. Nevertheless, the isolation and purification of concentrated populations of adipose-derived regenerative cells comprising adipose-derived stem cells (ADSCs), usually involves a series of washing, digestion, filtration and/or centrifugation steps, which can reduce the yield of viable cells, require mechanical equipment and specialized clinicians, and/or can compromise the quality, appearance, longevity, hydration or efficacy of the graft.
The need for additional approaches to prepare and optimize adipose tissue grafts and implants and to isolate and/or concentrate adipose-derived regenerative cells is manifest.